Numerical investigation of the effect of coefficient of friction on fixturing characteristics of freeform workpieces

In fixture, workpiece is positioned by locators and held at the position and orientation by the clamps. Frictional contact is established between the workpiece and locators.Measurement of the coefficient of friction between the workpiece and fixturing elements is a difficult to perform task due to the accessibility problems. The coefficient offriction plays an important role in fixturing of workpieces especially those with freefonn geometries. Although. designer may not consider the friction as an agent thatapplies kinematic constraint to the workpiece, it may affect the reaction forces at locators and workpiece deflection as well. In this study. numerical calculation has been conducted in order to study the effects of coefficient of friction on the output characteristics of the ftxturing process. The workpiece maximum deflection, reaction forces on the locating agents and displacements of the locating points were considered as the output parameters. By running several simulations in Abaqus software for a freeform sheet metal workpiece and alternating the coefficient of friction in interval of [0.5—0.8], it was concluded that the maximum deflection of workpiece, displacements of the locating points and reaction force values were not change in sensible manner. By assuming the frictionless contacts between the workpiece and locators, it was concluded that the values of the mentioned parameters change sensibly for the studied workpiece. So, it was generally concluded that the selection of the coefficient of friction in the cormnonly suggested intervals of contact between the locators and workpiece materials is not a crucial factor and the mean values may be chosen for the real industrial applications ensuring the appropriate results. Also. the assumption of frictionless contacts between the mated surfaces is unreasonable.

Keywords:

Coefficient of friction , fixture design , freeform workpiece , sheet metal part